Belt grinder



H. WEZEL BELT GRINDER Oct. 13, 1970 3 Sheets-'Sheet 1 Filed NGV. 28, 1967 /NVEN'OR H. WEZEL BELT GRINDER Oct. 13, 1970 25 Sheets-Sheet 2 Filed NOV. 28, 196'?I Har/7.5 Neze/ ATTRNE 5 Oct. 13, 1970 H. wEzEl. 3,533,192

BELT GRINDER Filed Nov. 28, 1967 3 Sheets-Sheet 5 /m/E/vrol? Hof/7s Neze/ United States Patent() U.S. Cl. 51-148 3 Claims ABSTRACT F THE DISCLOSURE A driving pulley is rotatably mounted in a frame and 1n contact with a grinding belt and power-operable to drive the same. A tensioning finger is carried by the frame and carries a roller in contact with the belt. The tensioning finger is disposed inside the belt and between the pulley and the roller. Spring means are provided to urge the roller against the belt to tension the same.

This invention relates to a belt grinder, which comprises a grinding belt extending from the driving pulley and in contact with one or more rollers and tensioned by spring action. This belt grinder is used mainly for machining straight and curved surfaces and recesses in the manufacture of tools and molds.

Known belt grinders comprise a grinding belt which contacts two or more rollers. In these known grinders, the spring-loaded roller carrier extends parallel to the vgrinding belt and is provided with two handles, one of which accommodates the drive unit. These belt grinders are relatively large so that they cannot be used for machining portions which are difficultly accessible, such as apertures and the like. The present invention provides a belt grinder which can be 'miniaturized The belt grinder comprising a grinding belt, which extends from a driving pulley and in contact with one or more rollers and which is tensioned by spring action, is characterized according to the invention in that the tension of the belt is maintained by means of an outwardly spring-urged finger, which extends between the rollers and the grinding belt so that the working portion of the grinding belt is exposed on all sides. The tensioning finger is detachably and pivotally screw-connected by means of an offset fixing eye disposed below the driving pulley. Hence, the tensioning finger is eccentric to the shaft of the driving pulley and is adjustable along an arc of a circle relative to said shaft. As a result, there are no protruding parts on both sides of the grinding belt and the grinding finger can easily be introduced into recesses and the like. Besides, an exchange 4between different fingers for various grinding operations is facilitated. For this purpose, the inside diameter of the fixing eye exceeds the diameter of the driving pulley to facilitate a replacement of the finger when the belt has been removed.

More specifically, where the shaft of the driving pulley extends at right angles to the main axis or motor axis, the resilient finger may extend parallel to the main axis. Alternatively, where the shaft of the driving pulley lies in the main axis or motor axis, the resilient finger is at right angles to the main axis. Furthermore, the tensioning finger may be telescopic and spring-loaded and the tensioning roller at the end of the finger may be laterally pivotally movable. This provides for a satisfactory positioning of the roller so that the grinding belt does not wander off the roller. For this purpose, the bracket mounted at the end of the finger and carrying the tensioning roller is pivotally movable against spring action by an adjustment of a screw.

Further embodiments of detachable tensioning fingers ice will be explained hereinafter with reference to the accompanying drawing, in which FIGS. 1 and 2, respectively, are a side elevation and top plan view showing a belt grinder according to the invention, partly in section.

FIGS. 3 to 5 are elevations showing various types of tensioning fingers.

As is apparent from FIGS. 1 and 2 of the drawings, a drive unit is accommodated in the handle 1. The handle is joined to a generally cylindrical frame 1a. An angle gearing 2 is journaled in frame 1a and drives a crossshaft 3, which carries a driving pulley 4 for the grinding belt 5. Pulley 4 is mounted in frame 1a and is coaxial therewith. 'Ihe drive unit may consist of a compressed-air motor, an electric motor or a driven flexible shaft. In the first embodiment, the grinding belt 5 extends around the roller 6 at the end of a tensioning finger 7, which is held extended in the pin-slot guide 9, 10 by the action of a spring 8. An eye 11 is engaged on frame 1a and is coaxial with pulley 4. Tensioning finger 7 is integral with and extends outwardly of the eye which is pivotally held under the driving pulley 4 by means of the nut 12 engaged on frame 1a. The replacement of the tensioning finger after the removal of the belt is facilitated in that the inside diameter of the fixing eye 11 exceeds the diameter of the driving pulley 4. The spring-loaded, telescopic tensioning finger 7 is entirely disposed inside the grinding belt 5 so that the Working portion of the latter is exposed on all sides. The tensioning roller 6 at the end of the tensioning finger 7 is laterally movable by the adjustment of a screw 14, which is operable to move the roller 6 about the pin 13 against the action of a spring 15 to adjust the belt to the proper running position without lateral wandering.

Further embodiments of replaceable tensioning fingers are shown in FIGS. 3 to 5. FIG. I3 shows an angled tensioning finger 16 and a grinding belt 17, which extends around the driving pulley 18, the deiiecting pulley 19 and the end pulley to form a triangle. In this case too the tensioning finger 16 is telescopic and has a guide 21 and is resiliently extended and the end roller 20 is laterally pivotally movable at 22. FIG. 4 shows an angled tensioning finger 23 and a grinding belt 24l, which extends around a driving pulley 25 and an end pulley 26. A curved leaf spring 27 is disposed at the bend of the finger. The grinding belt 24 wipes over this spring so that concave portions can be ground. A telescope spring is indicated at 28 and means for a lateral pivotal movement of the end roller at 29. Finally, FIG. 5 shows a tensioning finger 30, which is provided with a grinding belt 31, which runs around a driving pulley 32 and an end roller 33. The latter 1s carried by one end 34 of a leaf spring. The telescope spring is indicated at 35 and the means 36 for laterally pivotally moving the end roller 33 so as to adjust the proper running position of the belt and have the same construction as shown in FIG. 1. Other forms of the detachable tensioning finger may be used in the belt grinder according to the invention. That portion of the resilient finger which contacts the grinding belt may be convex or concave, depending on the form of the workpiece portion to be machined.

What is claimed is:

1. A belt grinder which comprises a generally cylindrical frame, a grinding belt, a driving pulley rotatably mounted in said frame and in contact with said belt, and power-operable to drive the belt, a roller in contact with the belt, a tensioning finger carried by and extending outwardly of said frame and carrying said roller, said tensioning finger being disposed inside the belt between the pulley and roller, spring means loading the roller to urge it against the belt to tension the belt, an eye on said frame carrying said tensioning finger,4said eye being disposed coaxially with said pulley, screw threaded means kdetachably and pivotally holding said eye to theframe coaxial with the pulley and a flexible leaf spring carried by said linger at the free end thereof and carrying said roller.

2. A belt grinder which comprises a generally cylindrical frame, a grinding belt, a driving pulley rotatably mounted in said frame and in contact with said belt, and power-operable to drive the belt, a roller in contact with the belt, a tensioning linger carried by and extending outwardly of said `frame and carrying said roller, said tensioning linger being disposed inside the belt between the pulley and roller, spring means loading the roller to urge it against the belt to tension the belt, an eye on said frame carrying said tensioning linger, said eye being disposed coaxially with said pulley, screw threaded means detachably and pivotally holding said eye to the frame coaxial with the pulley, said linger being formed with a bend near said grinding belt and a curved leaf spring being carried by said linger and disposed at said bend and in contact with said grinding belt.

3. A belt grinder which comprises a generally cylindrical frame, a grinding belt, a driving pulley rotatably mounted in said frame and in contact with said belt, and power-operable to drive the belt, a roller in contact with the belt, a tensioning linger carried by and extending outwardly of said frame and carrying said roller, said tensioning linger being disposed inside the belt between the pulley and roller, spring means loading the roller to urge it against the belt to tension the belt, an eye on said frame carrying said tensioning linger, saideye being disposed coaxially with said pulley, screw threaded means detachably and pivotally holding said eye to the frame coaxial with the pulley, said linger being formed with a bend near said grinding belt and having a free end portion, said roller being carried by said linger at said free end portion and an additional roller in contact with said belt and carried by said grinding linger at said bend.

References Cited ROBERT C. RIORDON, Primary Examiner 25 D. G. KELLY, Assistant Examiner U.S. Cl. X.R. 51-170 

